I'm not sure that I quite understand your question. Some people claim PIP when they are working, and others do not, but it is exactly the same benefit.
The DWP is not so interested in someone's medical condition/s - they are interested in how the condition/s impact on the claimant's daily life and mobility. Two people can appear to have the same condition, and one will be awarded PIP and another won't. The differences are usually down to things such as the severity of the condition, the type of medication/s, and the impact on their life against the specific PIP criteria. There is a test that your son can take to see if he might be eligible for PIP.
